Logs received in a sawmill vary in diameter and length. Some logs are straight, and others are far from straight and have a variety of physical shapes and deformities including taper, flared butts, hooks, crooks, branch stubs, branches, cat faces, splits, and loose bark. In some cases groups of logs are moved on a transverse conveyor sometimes one on top of the other or crossed and tangled in a way that makes them difficult to separate by normal means. Thus, a log sorter is provided so that the logs can be separated and regrouped into smaller groups or moved one at a time on an exit conveyor for grading and subsequent processing.
There are different types of log sorters. Rotary log sorters have drums that rotate with pockets or arms. Most of these rotate continuously and this continuous rotation can present a problem if crossed logs or curved logs are caught in a drum. Examples of such a sorter are U.S. Pat. Nos. 4,852,716 to Roche, and 5,011,024 to Bunney. Other types of log sorters include those which have discs or arms that pick up a log at several positions along its length. Such sorters sometimes have a crooked log or branch caught between the discs and jam-ups can occur in the sorting operation. Step sorters are also available which sort logs in a series of steps. One example of a step sorter is Canadian Patent 692,593 to Nienstedt. Other patents that relate to different types of sorters or singulators are U.S. Pat. Nos. 4,245,735; 4,624,361; 4,911,283 and 4,930,616.